This invention is directed to hair grooming and styling appliances and, in particular, to appliances which are used in conjunction with heat.
Human hair is considered to be built up from very complex protein called Alpha-Keratin. The protein molecules are arranged in organized patterns and are held together with hydrogen or sulfur bonds. These bonds determine the degree of curliness of hair.
The hydrogen bonds are the bonds which are broken and reformed when washing and setting hair. Breaking these bonds is accomplished by warm water, steam or heat, thus it is common for persons to wash their hair prior to reshaping a hairstyle. Moist hair, due to the breaking of these bonds, is very elastic and can be stretched and formed by various means. When dry, the hydrogen bonds reform and the hair is said to have taken a set. Dry hair does not stretch so rough handling such as rolling and vigorous combing should be avoided as damaged due to breakage is possible. Overly dried hair will become brittle and may suffer from such unrepairable conditions as split ends.
Hair, being hydroscopic, will absorb moisture from the atmosphere. Hair drying and styling appliances such as hair dryers, curling irons and styling brushes, because they are heated, provide an artificially dry condition for the hair. Hair can withstand high temperatures, but excessive dryness is known to cause damage even at low temperatures. U.S. Pat. No. 3,082,540 issued to Hiltenbrand, describes a hair dryer that measures the humidity of the air after it has passed over the user's head. U.S. Pat. No. 4,260,875 issued to Walter et al., describes a hair dryer that measures the temperature of the air deflected off the user's head while drying and may serve as a measure of dryness of the hair. U.S. Pat. No. 4,259,566 issued to Kobayashi, describes a hair waving appliance that uses plural independently temperature controllable heaters and plural temperature sensing probes which may therefore serve to measure the wetness/dryness of the user's hair.
British Patent No. 801,286, issued to Josef Vatter, describes a hair roller which is pre-positioned in the hair to be dried while using a drying hood. One or more pairs of teeth on the roller form electrodes; the resistance between these electrodes is constantly monitored during the drying process, and compared to a present value. A signal is output when the sensed resistance is at least as high as this value, to indicate the drying process as being complete. It is apparent that the method will sense the moisture content of the hair at only one location, and that there may be considerable variation in the degree of dryness of the hair at other locations. The roller was provided with insulating stand-off rings to prevent the electrodes from contacting the scalp.
In a dynamic hair grooming appliance, by which is meant an appliance in the nature of a brush or comb or curling iron which will be normally moved through the hair for the grooming and styling thereof while the hair is being dried, the provision of sensing electrodes will permit the dryness of the hair to be determined at any location. It is apparent that the provision of stand-off insulating rings will hinder the grooming of the hair, and would therefore be impractical.
A further problem exists in providing a dynamic hair grooming appliance for determining the dryness of the hair. It will be appreciated that an appliance of this nature will be frequently moved to a position out of contact with the hair, in which position of the electrodes will sense a dry hair condition. The generation of a signal responsive thereto would be both irritating and confusing, particularly where the signal is an audio signal.